1. Field of the Invention
The present invention relates to a servo controller for driving feed axes and rotation axes of drive mechanisms for machine tools, injection molding machines, press machines, etc., and more particularly, to a servo controller suited for a case where identical parts continue to be machined many times in a machine tool for parts machining.
2. Description of the Related Art
Learning control is known as a method to converge a control deviation to near zero, thereby improving the machining accuracy, in performing machining or the like in response to commands of identical patterns that are issued repeatedly. In this conventional learning control, as shown in FIG. 2, the identical patterns are repeatedly issued in fixed pattern periods. Correction data that is obtained in accordance with a position deviation in each control period in a preceding pattern period is previously stored in a learning memory. The position deviation is converged to zero by adding correction data for a control period corresponding to the preceding pattern period stored in the learning memory to the position deviation for each control period for the pattern period concerned (see Japanese Patent Applications Laid-open Nos. 7-104823 and 6-309021, for example).
The aforesaid learning control is applied to the case of a piston lathe in which commands are repeatedly executed for identical patterns for a profile. However, this learning control is not applicable to a case where the identical patterns are not repeatedly executed.
The learning control cannot be applied to a case where a lot of identical parts continue to be machined or identical shapes must be intermittently machined many times, although commands for machining the identical shapes have identical command patterns.